Sprengel; Camerarius; Kéolreuter 403 
my own observations on plants, guided to a certain extent by the 
experience of the breeders of animals, I became convinced many years 
ago that it is a general law of nature that flowers are adapted to be 
crossed, at least occasionally, by pollen from a distinct plant.” 
The experience of animal breeders pointed to the conclusion that 
continual in-breeding is injurious. If this is correct, it raises the 
question whether the same conclusion holds for plants. As most 
flowers are hermaphrodite, plants afford much more favourable 
material than animals for an experimental solution of the question, 
what results follow from the union of nearly related sexual cells as 
compared with those obtained by the introduction of new blood. 
The answer to this question must, moreover, possess the greatest 
significance for the correct understanding of sexual reproduction in 
general. 
We see, therefore, that the problems which Darwin had before 
him in his researches into the biology of flowers were of the greatest 
importance, and at the same time that the point of view from which 
he attacked the problems was essentially a teleological one. 
We may next inquire in what condition he found the biology of 
‘flowers at the time of his first researches, which were undertaken 
about the year 1838. In his autobiography he writes,—“ During the 
summer of 1839, and, I believe, during the previous summer, I was 
led to attend to the cross-fertilisation of flowers by the aid of insects, 
from having come to the conclusion in my speculations on the origin 
of species, that crossing played an important part in keeping specific 
forms constant”.” In 1841 he became acquainted with Sprengel’s 
work: his researches into the biology of flowers were thus continued 
for about forty years. 
It is obvious that there could only be a biology of flowers after 
it had been demonstrated that the formation of seeds and fruit in 
the flower is dependent on pollination and subsequent fertilisation. 
This proof was supplied at the end of the seventeenth century by R. J. 
Camerarius (1665—1721). He showed that normally seeds and fruits 
are developed only when the pollen reaches the stigma. The manner in 
which this happens was first thoroughly investigated by J. G. Kélreuter 
(1733—1806?), the same observer to whom we owe the earliest experi- 
ments in hybridisation of real scientific interest. Kolreuter mentioned 
that pollen may be carried from one flower to another partly by 
wind and partly by insects. But he held the view, and that was, 
1 Cross and Self fertilisation (1st edit.), p. 6. 
4 The Life and Letters of Charles Darwin, Vol. 1. p. 90, London, 1888. 
8 Kolreuter, Vorliufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden 
Versuchen und Beobachtungen, Leipzig, 1761; with three supplements, 1763—66. Also, 
Mém. de Vacad. St Pétersbourg, Vol. xv. 1809. 
26—2 
